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Disk drive with different synchronization fields and synchronization marks in the data sector preambles in adjacent data tracks

a technology of synchronization fields and disk drives, applied in the field of magnetic recording hard disk drives, can solve the problems of preventing the read head from achieving bit synchronization, jitter of the gate signal, and ensuring the ability to handle iti, so as to ensure the ability to detect iti. the effect of easy detection

Active Publication Date: 2015-03-17
WESTERN DIGITAL TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention relates to hard drives with data sector preambles that allow for inter-track interference (ITI) reduction. The preambles of data sectors in a track are different from each other and from adjacent tracks to prevent interference. The preambles can be "integrated," meaning they are a sequence of bits that does not include separate dedicated fields, and each track's preamble is different from nearby tracks. The read / write channel includes a matched filter for each unique preamble sequence to detect and calculate bit synchronization and start-of-data information. The preamble sequences are selected to have small autocorrelation and low cross-correlation to ensure effective inter-track interference reduction.

Problems solved by technology

However, the write gate signal may exhibit jitter so that the preambles in radially adjacent tracks are not precisely aligned circumferentially (i.e., in the along-the-track direction).
The result is that there can be track-to-track phase error, which can prevent the read head from achieving bit synchronization or achieving bit synchronization with the data sectors in the wrong data track.
An additional problem in achieving bit synchronization arises because of decreased track spacing and inherent track misregistration (TMR) during reading and writing.
Also, because the heads cannot be precisely positioned radially, there is always some TMR during reading and writing.
The problems caused by write gate jitter, TMR and track squeeze can result in significant inter-track interference (ITI).
If ITI is too great, reliable acquisition of synchronization is not possible or the read head may incorrectly synchronize with data sectors in an adjacent data track.

Method used

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  • Disk drive with different synchronization fields and synchronization marks in the data sector preambles in adjacent data tracks
  • Disk drive with different synchronization fields and synchronization marks in the data sector preambles in adjacent data tracks
  • Disk drive with different synchronization fields and synchronization marks in the data sector preambles in adjacent data tracks

Examples

Experimental program
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first embodiment

[0038]In embodiments of this invention the same data sector preamble is used for all data sectors in a track but the preamble in each track is different from the preamble in radially adjacent tracks. In a first embodiment each SF in each track is different from the SF in radially adjacent tracks, and each SM in each track is different from the SM in radially adjacent tracks. Thus only two unique SFs and two unique SMs are required, with the two SFs and two SMs alternating in radially adjacent tracks. If there are only two SFs, then for example one SF can be a 2T frequency and the other SF can be either a periodic 2.5T frequency (a pattern of positive magnetization for 2.5T followed by a negative magnetization for 2.5T) or a periodic 3T frequency (a pattern of positive magnetization for 3T followed by a negative magnetization for 3T). While at least two unique SFs and two unique SMs are required, preferably there are at least three unique SFs and three unique SMs that periodically re...

second embodiment

[0046]FIG. 10 is a high-level block diagram of the read / write channel electronics for explaining the read process with the The HDC receives the LBAs to be read from the host and calculates the CHS for the PBAs corresponding to the LBAs. The HDC can also determine, from the cylinder portion of the CHS (i.e., the physical target track where the data blocks are to be read) the sequence number, i.e., whether sequence 1, 2, or 3 is to be read before the data blocks are read. This is a straightforward modulo 3 of the target track number. Alternatively, the channel can determine the sequence number from the cylinder number. In either case the channel identifies the unique sequence to be read. The HDC issues a seek command to the servo electronics to cause the read head to seek to the target track. When the read head is at the target track, the HDC sends a read gate (RG) high signal to the read / write channel. The sequence preceding the target data sector in the target track is then read an...

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Abstract

A hard disk drive has disks with data sector preambles that allow for inter-track interference. The same data sector preamble is used for all data sectors in a track but the preamble in each track is different from the preamble in radially adjacent tracks. In a first embodiment each preamble includes a synchronization field (SF) and synchronization mark (SM) that are the same in each track but different from the SF and SM in radially adjacent tracks. Only two unique SFs and two unique SMs are required, with the two SFs and two SMs alternating in radially adjacent tracks. In a second embodiment the preambles are “integrated”, meaning that the preamble is a sequence of bits that does not include separate dedicated fields, like SF and SM. The preamble bit sequences are decoded using matched filters to provide bit synchronization and start-of-data information.

Description

RELATED APPLICATION[0001]This application is related to application Ser. No. 14 / 031,989 filed Sep. 19, 2013 titled “DISK DRIVE WITH DIFFERENT DATA SECTOR INTEGRATED PREAMBLES IN ADJACENT DATA TRACKS” and assigned to the same assignee as this application.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to magnetic recording hard disk drives (HDDs), and more particularly to a HDD with improved reading of data in the presence of inter-track interference (ITI).[0004]2. Description of the Related Art[0005]In HDDs, data is written in angularly spaced data sectors in the concentric data tracks of the recording layers on the disks. A data sector preamble precedes each data sector and is written each time data is written in the data sector. The preamble includes a synchronization field (SF) for achieving bit synchronization and a synchronization mark (SM) for indicating the start of the data sector. The writing of the preamble and the data is i...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G11B5/09G11B20/12
CPCG11B20/1217G11B2020/1232
Inventor COKER, JONATHAN DARRELGALBRAITH, RICHARD LEOHANSON, WELDON MARKOENNING, TRAVIS ROGERSURENDRAN, SRINIVASAN
Owner WESTERN DIGITAL TECH INC
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